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Tackling the dengue crisis with science

  • Published at 12:04 am September 20th, 2019
Dengue Mosquito
Photo: BIGSTOCK

Science-driven pro-active measures can bring us closer to a solution

Dengue has been endemic for decades in Bangladesh. The disease has been prevalent in this sub-continent for years. Naturally, Bangladesh was not spared. 

Dengue season lasts from April to October, but studies prove otherwise. It is found to be prevalent all year round, albeit turns menacing during April-October.  

Dengue fever is spread by the female of the species. A very special characteristic of female Aedes aegypti mosquitoes is that a range of light intensity stimulates their biting or intrinsic urges, and hence they have been found to be biting most during early hours after sunrise and before sunset. 

In the dark, however, no conspicuous host-seeking activity is observed. The light-intensity stimulation characteristic of Aedes mosquitoes’ biting habit complicates the preventive and containment strategy in today’s context. 

People in their homes are usually casually dressed with more surface area of the human body exposed and accessible to landing Aedes mosquitoes. Therefore, the number of female Aedes per person can increase transmission by multiple feedings during these opportune periods of human presence and possible inactivity (eg watching television, computing, or having dinner). 

Children attending schools at early hours of the day also become vulnerable to biting by Aedes mosquitoes. As a result, we have the highest percentage of dengue patients in the 15-35 year-age-group this year. Therefore, the increase in street lighting, use of dusk to dawn external security lighting, and use of other internal light fittings in houses increase light intensities that mimic conditions similar to daylight/twilight within homes, thereby providing suitable conditions to extend the hours of landing activity of dengue vectors.

Entomological studies in Bangladesh, although not routinely done, identified presence of mosquito vector Aedes aegypti and A albopictus not only in Dhaka city, but also in other metropolitan areas of Bangladesh. Aedes aegypti were found even in the stagnant, dirty drain water in Azimpur orphanage premises. This highlights the adaptability of dengue vectors to the changing environment. 

Periodic and year-long entomological surveys should be conducted all over the country, given the fact that Aedes mosquitoes can adopt and develop in different environmental conditions as mentioned before. The entomological findings will pinpoint the breeding places of Aedes mosquitoes, and help towards eradicating breeding places, and may prove as a most effective tool against dengue vectors.

This year, the DenV-3 sub-type is prevalent, which is different from that of the previous year, with mortality over 100 and morbidity in the thousands, breaking all previous records. 

An early virological study will signal the possible severity of dengue disease process, if found different from sub-types of DenV from the previous year. The authorities concerned will be able to chalk-up training programs for the health personnel, as well as, create awareness for the general people.

A sustainable cleaning program all year round is necessary. Destruction of breeding places, not only the fresh-water containers but also the dirty, stagnant waters in drains and other places, should be the main target of the program.

Without getting the general masses into action, authorities concerned cannot fight off the dengue menace. The awareness program must be run throughout the year, using all possible means. Health messages should be aired in places where people gather in numbers. Local government agencies and social organizations should be involved in awareness programs against dengue.

Every year, we see the digging and repairing of roads, drains, and pavements start from June, the last month of the financial year. It’s the result of delayed project plans, long tendering processes, and release of project funds at the fag end. And the rainy season starts from June, causing not only low quality works, washing away construction and repair materials, but it also contributes to the stagnation of water in the pot-holes and clogged drains. Can’t the government introduce the financial year from January? 

Poly-bags were banned way back in 2002 to reduce pollution and encourage the use of environment-friendly alternatives. But this very pragmatic law has never been strictly implemented. The government should not enact a law that it cannot implement. The poly-bags remain a very big source of breeding places for Aedes mosquitoes. 

Finally, we need pro-active, fast-acting, and efficient managers, in this case mayors, in city corporations. One may easily point a finger at the utter failure on their part. They miserably failed to anticipate the dengue menace, despite being well-informed in advance. 

MM Mortayez Amin is a consultant at the National Healthcare Network of the Diabetic Association of Bangladesh. He can be reached at [email protected]